The reason that most homebrewers prefer liquid yeast is that liquid
yeasts are usually a purer strain that dry yeast. This has a lot to
do with how the two forms are made. I recommend the Zymurgy special
issue on yeast for a more detailed explanation.

Personally, I prefer to use liquid yeast. I've made decent beer with
dry yeast, but the overall quality of my beers made with liquid yeast
is _MUCH_ better.